Circuit for physical quantity detection device, physical quantity detection device, electronic apparatus, and moving object

ABSTRACT

A circuit for a physical quantity detection device includes a drive unit that generates a drive signal that causes an vibrator to vibrate, a detection unit that detects a detection signal outputted from the vibrator based on the drive signal, a passive filter which has a filter characteristic in which a cutoff frequency is lower than a detuning frequency and a cutoff frequency band contains a frequency band higher than the cutoff frequency and to which a signal from the detection unit is inputted, and an amplification unit that amplifies a signal from the passive filter.

BACKGROUND

1. Technical Field

The present invention relates to a circuit for a physical quantitydetection device, a physical quantity detection device, an electronicapparatus, and a moving object.

2. Related Art

There is a known physical quantity detection device that detects aphysical quantity, such as angular velocity and acceleration, by usingan vibrator, such as a quartz vibrator (piezoelectric vibrator) and anMEMS (micro electromechanical systems) vibrator.

In an angular velocity detection device, for example, in which thefrequency at which an vibrator is driven and the frequency at whichangular velocity is detected typically differ from each other, when adetection signal outputted from the vibrator is detected by using adrive signal, a detuning frequency component formed of a detuningfrequency, which is the difference between the drive frequency and thedetection frequency, is produced as an undesired wave. When the detuningfrequency component increases, for example, because an impact having alarge magnitude acts on the angular velocity detection device,saturation occurs in a downstream amplification circuit, resulting in anincorrect output result in some cases.

JP-A-2008-256668 discloses an angular velocity sensor including a noiseremover that includes an active filter and removes a detuning frequencycomponent from a signal having undergone synchronous detection in asynchronous detector.

In the configuration disclosed in JP-A-2008-256668, in which the activefilter is provided in a position upstream of an amplifier, noiseresulting from a transistor in the active filter is produced in aportion upstream of the amplifier. As a result, the noise produced inthe active filter is undesirably amplified by the amplifier andoutputted.

SUMMARY

An advantage of some aspects of the invention is to provide a circuitfor a physical quantity detection device, a physical quantity detectiondevice, an electronic apparatus, and a moving object capable ofsuppressing a detuning frequency component with noise resulting from afilter suppressed.

Application Example 1

This application example is directed to a circuit for a physicalquantity detection device including a drive unit that generates a drivesignal that causes an vibrator to vibrate, a detection unit that detectsa detection signal outputted from the vibrator based on the drivesignal, a passive filter which has a filter characteristic in which acutoff frequency is lower than a detuning frequency and a cutofffrequency band contains a frequency band higher than the cutofffrequency and to which a signal from the detection unit is inputted, andan amplification unit that amplifies a signal from the passive filter.

According to this application example, the passive filter, which has afilter characteristic in which a cutoff frequency is lower than adetuning frequency and a cutoff frequency band contains a frequency bandhigher than the cutoff frequency and to which a signal from thedetection unit is inputted, can suppress a detuning frequency componentcontained in the signal from the detection unit. Further, a passivefilter does not produce noise resulting from a transistor, whereby noiseresulting from the filter can be suppressed as compared with a casewhere an active filter is used.

Application Example 2

In the circuit for a physical quantity detection device according to theapplication example described above, it is preferable that the cutofffrequency is one-half the detuning frequency or lower.

According to this application example, the detuning frequency componentcontained in the signal outputted from the detection unit can further besuppressed.

Application Example 3

In the circuit for a physical quantity detection device according to theapplication example described above, it is preferable that the passivefilter is a first-order CR filter.

According to this application example, the passive filter can beconfigured by using a simple circuit configuration.

Application Example 4

In the circuit for a physical quantity detection device according to theapplication example described above, it is preferable that the passivefilter is a second-order or higher-order CR filter.

According to this application example, a filter characteristic thatallows sharper attenuation in the frequency band higher than the cutofffrequency than the degree of attenuation provided by a first-order CRfilter, whereby the detuning frequency component can be effectivelysuppressed.

Application Example 5

It is preferable that the circuit for a physical quantity detectiondevice according to the application example described above furtherincludes a filter unit that filters a signal outputted from theamplification unit.

According to this application example, the detuning frequency componentcan further be suppressed in a portion downstream of the amplificationunit. Further, a harmonic component produced when the detection unitperforms detection can be suppressed. Moreover, for example, when thefilter unit is formed of a switched capacitor filter, the passive filterupstream of the amplification unit is allowed to also function as ananti-alias filter for the filter unit.

Application Example 6

It is preferable that the circuit for a physical quantity detectionaccording to the application example device described above furtherincludes a semiconductor substrate, a wiring line that is provided inthe semiconductor substrate and electrically connects the passive filterand the amplification unit to each other, and a first shield wiring linethat is so provided in the semiconductor substrate that the first shieldwiring line is separated from the wiring line and juxtaposed to at leastpart of the wiring line in a plan view.

According to this application example, the provision of the first shieldwiring line prevents extraneous noise from entering the signal inputtedto the amplification unit.

Application Example 7

It is preferable that the circuit for a physical quantity detectiondevice according to the application example described above furtherincludes a second shield wiring line that is so provided in thesemiconductor substrate that the second shield wiring line is separatedfrom the wiring line and juxtaposed to at least part of the wiring linein a plan view, wherein the at least part of the wiring line is disposedbetween the first shield wiring line and the second shield wiring linein the plan view.

According to this application example, since the wiring line, whichconnects the passive filter and the amplification unit to each other, isprovided between the first shield wiring line and the second shieldwiring line, the shield wiring lines can further prevent extraneousnoise from entering the signal inputted to the amplification unit.

Application Example 8

It is preferable that the circuit for a physical quantity detectiondevice according to the application example described above furtherincludes a third shield wiring line that is so provided in thesemiconductor substrate that the third shield wiring line is separatedfrom the wiring line and overlaps with at least part of the wiring linein a plan view.

According to this application example, the provision of the third shieldwiring line can further prevent extraneous noise from entering thesignal inputted to the amplification unit.

Application Example 9

It is preferable that the circuit for a physical quantity detectiondevice according to the application example described above furtherincludes a guard ring so provided in the semiconductor substrate thatthe guard ring surrounds part of a circuit accommodated in the circuitfor a physical quantity detection device in a plan view, wherein atleast one of the first shield wiring line, the second shield wiringline, and the third shield wiring line is electrically connected to theguard ring.

According to this application example, since at least one of the firstshield wiring line, the second shield wiring line, and the third shieldwiring line is electrically connected to the guard ring, which istypically electrically connected to a stable potential, the wiring line,which electrically connects the passive filter and the amplificationunit to each other, can be shielded and kept at a stable potential.

Application Example 10

This application example is directed to a physical quantity detectiondevice including any of the circuits for a physical quantity detectiondevice according to the application examples described above and anvibrator.

According to this application example, the physical quantity detectiondevice, which includes the circuit for a physical quantity detectiondevice capable of suppressing a detuning frequency component with noiseresulting from a filter suppressed, can be highly reliable in operation.

Application Example 11

This application example is directed to an electronic apparatusincluding any of the circuits for a physical quantity detection deviceaccording to the application examples described above or the physicalquantity detection device according to the application example describedabove.

Application Example 12

This application example is directed to a moving object including any ofthe circuits for a physical quantity detection device according to theapplication examples described above or the physical quantity detectiondevice according to the application example described above.

The electronic apparatus and the moving object according to theseapplication examples, each of which includes the circuit for a physicalquantity detection device capable of suppressing a detuning frequencycomponent with noise resulting from a filter suppressed, can be highlyreliable in operation.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described with reference to the accompanyingdrawings, wherein like numbers reference like elements.

FIG. 1 is a circuit block diagram showing an example of a physicalquantity detection device according to an embodiment of the invention.

FIG. 2 is a plan view showing an example of an vibrator.

FIG. 3 is another plan view showing the example of an vibrator.

FIGS. 4A and 4B are circuit diagrams showing examples of theconfiguration of a passive filter.

FIG. 5A is a plan view diagrammatically showing part of a circuit for aphysical quantity detection device according to the present embodiment.FIG. 5B is a diagrammatic enlarged cross-sectional view taken along theline A-A′ in FIG. 5A.

FIG. 6 is a functional block diagram of an electronic apparatusaccording to the present embodiment.

FIG. 7 shows an example of the exterior appearance of a smartphone as anexample of the electronic apparatus.

FIG. 8 shows (is a top view showing) an example of a moving objectaccording to the present embodiment.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

A preferable example of the invention will be described below in detailwith reference to the drawings. The drawings to be used are provided forease of description. The example described below is not intended toinappropriately limit the contents of the invention set forth in theappended claims. Further, all the components described below are notnecessarily essentially required in the invention.

1. Physical Quantity Detection Device and Circuit for Physical QuantityDetection Device

FIG. 1 is a circuit block diagram showing an example of a physicalquantity detection device 1 according to an embodiment of the invention.The following description will be made with reference to the physicalquantity detection device 1 that detects angular velocity as an exampleof a physical quantity, but the physical quantity is not limited toangular velocity and may be acceleration or any one of a variety ofother physical quantities.

The physical quantity detection device 1 according to the presentembodiment includes an vibrator 10 and a circuit 5 for a physicalquantity detection device. The circuit 5 for a physical quantitydetection device may be configured as one or more semiconductor circuitdevices.

1-1. Vibrator

The vibrator 10 vibrates when excited based on a drive signal inputtedthrough a drive terminal 13 and a drive terminal 14, and the vibrator 10receives a Coriolis force when angular velocity motion acts on thevibrator 10 in the excited vibrating state. The vibrator 10 then outputsa detection signal containing an angular velocity component based on theCoriolis force.

FIGS. 2 and 3 are plan views showing an example of the vibrator 10. Thefollowing description will be made with reference to a case where thevibrator 10 is formed of a thin plate made of quartz or any otherpiezoelectric material, but the vibrator 10 is not necessarilyconfigured this way and may, for example, be an MEMS vibrator.

The vibrator 10 has drive bases 44, from each of which drive vibratingarms 11 (drive vibrating pieces in a broad sense) extend in a Y-axisdirection of the quartz. Each of the drive bases 44 is connected to adetection base 49 via a connection arm 45, which extends in an X-axisdirection of the quartz. Detection vibrating arms 12 (detectionvibrating pieces in a broad sense) extend from the detection base 49 inthe Y-axis direction.

Each of the detection vibrating arms 12 is provided with a detectionterminal 15, a detection terminal 16, and a ground terminal 17, and thedetection terminal 15 and the detection terminal 16 are connected to adetection circuit 30. The detection terminal 15 and the detectionterminal 16 are configured to output detection signals having phasesopposite to each other.

When a drive signal formed of an alternate voltage and an alternatecurrent is applied between a drive electrode 41 on a side surface ofeach of the drive vibrating arms 11 and a drive electrode 42 on theupper surface of the drive vibrating arm 11, a resultant piezoelectriceffect causes the drive vibrating arms 11 to undergo bending vibratingas indicated by the arrows B. In this state, when the vibrator 10rotates around a Z axis of the quartz or an axis of rotation as shown inFIG. 3, the drive vibrating arms 11 receive a Coriolis force in thedirection perpendicular to not only the bending vibrating directionindicated by the arrows B but also the Z axis. As a result, theconnection arms 45 vibrate as indicated by the arrows C. The detectionvibrating arms 12 along with the connection arms 45 then undergo bendingvibrating as indicated by the arrows D in response to the vibrating ofthe connection arms 45 (arrows C).

An inverse piezoelectric effect produced based on the bending vibratingdescribed above generates an alternate voltage and an alternate currentbetween a detection electrode 47 on a side surface of each of thedetection vibrating arms 12 and a detection electrode 46 on the uppersurface of the detection vibrating arm 12. One of the detectionelectrode 47 on the side surface of the detection vibrating arm 12 andthe detection electrode 46 on the upper surface thereof is connected tothe ground terminal 17, and the other detection electrode is connectedto the detection terminal 15 and the detection terminal 16. A detectionsignal containing an angular velocity component based on the Coriolisforce is outputted to the detection terminal 15 and the detectionterminal 16.

In the configuration shown in FIGS. 2 and 3, the detection base 49 isdisposed at the center and the detection vibrating arms 12 are extendedfrom the detection base 49 in opposite directions or in the +Y-axis and−Y-axis directions so that the vibrator 10 is balanced well. Further,the connection arms 45 are extended from the detection base 49 inopposite directions or in the +X-axis and −X-axis directions, and thedrive vibrating arms 11 are extended from each of the connection arms 45in opposite directions or in the +Y-axis and −Y-axis directions.

Further, a front end portion of each of the drive vibrating arms 11 isenlarged in the width direction thereof to form a large width portion43, to which a weight is further added, whereby a Coriolis force havinga large magnitude is produced. Moreover, the weight provides an effectof achieving a desired resonance frequency with the drive vibrating armshortened. From the same reason, a front end portion of each of thedetection vibrating arms 12 is enlarged in the width direction thereofto form a large width portion 48, to which a weight is further added.

The vibrator 10 is not necessarily configured as described above andonly needs to be an vibrator that outputs a detection signal containingan angular velocity component based on a Coriolis force. For example,the vibrator 10 may have a configuration in which the drive vibratingarms also serve as the detection vibrating arms or a configuration inwhich a piezoelectric film is formed on each of the drive vibrating armsand the detection vibrating arms.

1-2. Circuit for Physical Quantity Detection Device

The circuit 5 for a physical quantity detection device according to thepresent embodiment includes a drive unit 20, which generates a drivesignal that causes the vibrator 10 to vibrate, a detection unit 31,which detects a detection signal outputted from the vibrator 10 based onthe drive signal, a passive filter 32, which has a filter characteristicin which a cutoff frequency fc is lower than a detuning frequency fm andthe cutoff frequency band contains a frequency band higher than thecutoff frequency fc and to which a signal from the detection unit 31 isinputted, and an amplification unit 33, which amplifies a signal fromthe passive filter 32.

The drive unit 20 generates a drive signal that causes the vibrator 10to vibrate. More specifically, the drive unit 20 outputs the drivesignal to drive the vibrator 10 and excites the vibrator 10 to vibratewhen the drive unit 20 receives a feedback signal from the vibrator 10.

The drive unit 20 in the present embodiment includes a current-voltageconverter 21, an AC amplifier 22, an automatic gain control circuit 23,and a comparator 24.

When the drive vibrating arms 11 vibrate, a current based on apiezoelectric effect is outputted as a feedback signal through the driveterminal 14 and inputted to the current-voltage converter 21. Thecurrent-voltage converter 21 outputs an AC voltage signal having thesame frequency as the vibrating frequency of the drive vibrating arms11.

The AC voltage signal outputted from the current-voltage converter 21 isinputted to the AC amplifier 22. The AC amplifier 22 amplifies theinputted AC voltage signal.

The AC voltage signal outputted from the AC amplifier 22 is inputted tothe automatic gain control circuit 23. The automatic gain controlcircuit 23 performs gain control in such a way that the amplitude of theinputted AC voltage signal is held at a fixed value and outputs the ACvoltage signal having undergone the gain control to the drive terminal13. The AC voltage signal inputted to the drive terminal 13 drives thevibrator 10.

The AC voltage signal amplified by the AC amplifier 22 is also inputtedto the comparator 24, which outputs a square-wave voltage signal to thedetection unit 31. The output level of the square-wave voltage signal isswitched in accordance with a result of comparison between the ACvoltage signal and a reference voltage signal having a central value ofthe amplitude of the AC voltage signal.

The detection unit 31 detects the detection signal outputted from thevibrator 10 based on the drive signal. The detection unit 31 in thepresent embodiment includes a charge amplifier 311, a charge amplifier312, a differential amplifier 313, an AC amplifier 314, and asynchronous detection circuit 315.

The charge amplifier 311 and the charge amplifier 312 are connected tothe detection terminal 15 and the detection terminal 16, respectively,and receive detection signals having phases opposite to each other.Signals having undergone charge-voltage conversion in the chargeamplifier 311 and the charge amplifier 312 are inputted to thedifferential amplifier 313. The differential amplifier 313 performsdifferential amplification in which (output signal from charge amplifier311)−(output signal from charge amplifier 312) is amplified. The outputsignal from the differential amplifier 313 is further amplified by theAC amplifier 314. The amplification in each of the charge amplifier 311and the charge amplifier 312 advances the phase of the signal outputtedtherefrom by 90 degrees.

The synchronous detection circuit 315 performs synchronous detection ofthe output signal from the AC amplifier 314 based on the square-wavevoltage signal outputted from the comparator 24 to extract the angularvelocity component contained in the detection signal. Now, let f1 be theresonance frequency of the drive vibrating arms 11 and f2 be theresonance frequency of the detection vibrating arms 12. The outputsignal from the synchronous detection circuit 315 particularly containsa (f2−f1) frequency (detuning frequency fm) component as a detuningfrequency component (noise component).

The passive filter 32 filters the signal outputted from the detectionunit 31. The passive filter 32 has a filter characteristic in which thecutoff frequency fc is lower than the detuning frequency fm and thecutoff frequency band contains a frequency band higher than the cutofffrequency fc. The passive filter 32 can, for example, be a lowpassfilter or a band elimination filter. In the present embodiment, thepassive filter 32 is a lowpass filter. The passive filter 32 may have afunction of removing a harmonic component produced when the synchronousdetection circuit 315 performs detection.

The amplification unit 33 amplifies the signal outputted from thepassive filter 32. The amplification unit 33 may be an amplifier capableof controlling the amplification factor thereof. The detectionsensitivity of the physical quantity detection device 1 can thus beadjusted.

According to the present embodiment, the passive filter 32, which has afilter characteristic in which the cutoff frequency fc is lower than thedetuning frequency fm and the cutoff frequency band contains a frequencyband higher than the cutoff frequency fc and to which the signal fromthe detection unit 31 is inputted, can suppress the detuning frequencycomponent contained in the signal from the detection unit 31. Therefore,when the detuning frequency component increases due, for example, to animpact having a large magnitude and acting on the physical quantitydetection device 1, a risk of saturation in the amplification unit 33can be lowered, whereby the physical quantity detection device 1 can behighly reliable. Further, the passive filter 32 does not produce noiseresulting from a transistor, whereby noise resulting from the filter canbe suppressed as compared with a case where an active filter is used.

The cutoff frequency fc of the passive filter 32 may be one-half thedetuning frequency fm or lower.

According to the present embodiment, the detuning frequency componentcontained in the signal outputted from the detection unit 31 can furtherbe suppressed.

For example, when the detuning frequency fm is 600 Hz and the passivefilter 32 is formed of a first-order CR filter (lowpass filter),comparison based on a numerical simulation of the output from theamplification unit 33 between a case where the cutoff frequency fc ofthe passive filter 32 is set at 277 Hz (Example) and a case where thecutoff frequency fc is set at 3 kHz (Comparative Example) ascertainsthat the amount of detuning frequency component contained in the outputin Example is about 0.41 times the amount of contained detuningfrequency component in Comparative Example.

FIGS. 4A and 4B are circuit diagrams showing examples of theconfiguration of the passive filter 32.

The passive filter 32 may be a first-order CR filter. In the exampleshown in FIG. 4A, the passive filter 32 is formed of a first-orderlowpass filter including a resistor R1 and a capacitor C1. According tothe present embodiment, the passive filter 32 can be configured by usinga simple circuit configuration.

The passive filter 32 may be a second-order or higher-order CR filter.In the example shown in FIG. 4B, the passive filter 32 is formed of asecond-order lowpass filter including a resistor R1, a resistor R2, acapacitor C1, and a capacitor C2. According to the present embodiment, afilter characteristic that allows sharper attenuation in the frequencyband higher than the cutoff frequency fc than the degree of attenuationprovided by the first-order CR filter, whereby the detuning frequencycomponent can be effectively suppressed.

The circuit 5 for a physical quantity detection device according to thepresent embodiment may further include a filter unit 34, which filtersthe signal outputted from the amplification unit 33. The filter unit 34may, for example, be a lowpass filter or a band elimination filter. Thefilter unit 34 may instead be formed of an active filter, such as aswitched capacitor filter. The filter unit 34 may have a filtercharacteristic that allows suppression of the detuning frequencycomponent. The filter unit 34 may also have a filter characteristic thatallows suppression of a harmonic component produced when the synchronousdetection circuit 315 performs detection.

According to the present embodiment, the detuning frequency componentcan further be suppressed in a portion downstream of the amplificationunit 33. Further, a harmonic component produced when the detection unit31 performs detection can be suppressed. Moreover, for example, when thefilter unit 34 is formed of a switched capacitor filter, the passivefilter 32 upstream of the amplification unit 33 is allowed to alsofunction as an anti-alias filter for the filter unit 34.

The circuit 5 for a physical quantity detection device according to thepresent embodiment may further include a DC amplifier 35, a ratiometricamplifier 36, a lowpass filter 37, a buffer amplifier 38, and an outputterminal 39.

The DC amplifier 35 amplifies the output signal from the filter unit 34.The DC amplifier 35 may be an amplifier capable of controlling theamplification factor thereof. The detection sensitivity of the physicalquantity detection device 1 can thus be adjusted.

The ratiometric amplifier 36 amplifies the output signal from the DCamplifier 35. The ratiometric amplifier 36 is configured to have aratiometric characteristic that allows the amplification factor of theratiometric amplifier 36 to be changed in response to a change in powersupply voltage.

The lowpass filter 37 filters the output signal from the ratiometricamplifier 36. The lowpass filter 37 may have a filter characteristicthat allows suppression of the detuning frequency component. Further,the lowpass filter 37 may have a filter characteristic that allowssuppression of a harmonic component produced when the synchronousdetection circuit 315 performs detection.

The buffer amplifier 38 causes the output signal from the lowpass filter37 to undergo impedance conversion and outputs the converted signal tothe output terminal 39.

FIG. 5A is a plan view diagrammatically showing part of the circuit 5for a physical quantity detection device according to the presentembodiment. FIG. 5B is a diagrammatic enlarged cross-sectional viewtaken along the line A-A′ in FIG. 5A.

The circuit 5 for a physical quantity detection device according to thepresent embodiment may further include a semiconductor substrate 50, awiring line 321, which is provided in the semiconductor substrate 50 andelectrically connects the passive filter 32 and the amplification unit33 to each other, and a first shield wiring line S1, which is soprovided in the semiconductor substrate 50 that the first shield wiringline S1 is separated from the wiring line 321 but juxtaposed to at leastpart of the wiring line 321 in a plan view.

In the example shown in FIG. 5A, the synchronous detection circuit 315,the passive filter 32, and the amplification unit 33 are provided in thesemiconductor substrate 50. A wiring line 3151, which electricallyconnects the synchronous detection circuit 315 and the passive filter 32to each other, and the wiring line 321, which electrically connects thepassive filter 32 and the amplification unit 33 to each other, areprovided in the semiconductor substrate 50. Further, a potential wiringline to which a ground potential, a power supply potential, or any otherstable potential is supplied is provided in the semiconductor substrate50. The open arrows in FIG. 5A indicate the flow of a signal. In thepresent embodiment, a ground potential is supplied to the potentialwiring line.

In the example shown in FIG. 5B, the potential wiring line is formed ofmetal wiring lines in three layers with an interlayer insulating filmtherebetween and via conductors that electrically connect the wiringlines in wiring layers adjacent to each other.

The first shield wiring line S1 is so disposed that it is separated andinsulated from the wiring line 321. The first shield wiring line S1 isfurther so disposed that it is juxtaposed to at least part of the wiringline 321 in a plan view. In the example shown in FIG. 5B, the firstshield wiring line S1 is disposed in the wiring layer where the wiringline 321 is disposed.

According to the present embodiment, the provision of the first shieldwiring line S1 prevents extraneous noise from entering the signalinputted to the amplification unit 33. A risk of saturation in theamplification unit 33 due to extraneous noise can therefore be lowered,whereby the physical quantity detection device 1 can be highly reliable.

The circuit 5 for a physical quantity detection device according to thepresent embodiment may further include a second shield wiring line S2,which is so provided in the semiconductor substrate 50 that the secondshield wiring line S2 is separated from the wiring line 321 butjuxtaposed to at least part of the wiring line 321 in a plan view, andat least part of the wiring line 321 may be disposed between the firstshield wiring line S1 and the second shield wiring line S2 in the planview.

The second shield wiring line S2 is so disposed that it is separated andinsulated from the wiring line 321. The second shield wiring line S2 isfurther so disposed that it is juxtaposed to at least part of the wiringline 321 in a plan view. In the example shown in FIG. 5B, the secondshield wiring line S2 is disposed in the wiring layer where the wiringline 321 and the first shield wiring line S1 are disposed.

According to the present embodiment, since the wiring line 321, whichconnects the passive filter 32 and the amplification unit 33 to eachother, is provided between the first shield wiring line S1 and thesecond shield wiring line S2, the shield wiring lines can furtherprevent extraneous noise from entering the signal inputted to theamplification unit 33. A risk of saturation in the amplification unit 33due to extraneous noise can therefore be lowered, whereby the physicalquantity detection device 1 can be highly reliable.

The circuit 5 for a physical quantity detection device according to thepresent embodiment may further include a third shield wiring line S3,which is so provided in the semiconductor substrate 50 that the thirdshield wiring line S3 is separate from the wiring line 321 but overlapswith at least part of the wiring line 321 in a plan view.

The third shield wiring line S3 is so disposed that it is separated andinsulated from the wiring line 321. The third shield wiring line S3 isfurther so disposed that it overlaps with at least part of the wiringline 321 in a plan view. In the example shown in FIG. 5B, the thirdshield wiring line S3 is disposed in a wiring layer separate from thewiring line 321 toward the semiconductor substrate 50, but the twowiring lines are not necessarily disposed as described above and thewiring line 321 may be disposed in a wiring layer separate from thethird shield wiring line S3 toward the semiconductor substrate 50.

According to the present embodiment, the provision of the third shieldwiring line S3 can further prevent extraneous noise from entering thesignal inputted to the amplification unit 33. A risk of saturation inthe amplification unit 33 due to extraneous noise can therefore belowered, whereby the physical quantity detection device 1 can be highlyreliable.

The circuit 5 for a physical quantity detection device may furtherinclude a guard ring 51, which is so provided in the semiconductorsubstrate 50 that the guard ring 51 surrounds part of a circuit (circuitX) accommodated in the circuit 5 for a physical quantity detectiondevice in a plan view, and at least one of the first shield wiring lineS1, the second shield wiring line S2, and the third shield wiring lineS3 may be electrically connected to the guard ring 51. In the exampleshown in FIG. 5B, the first shield wiring line S1, the second shieldwiring line S2, and the third shield wiring line S3 are electricallyconnected to each other and each electrically connected to the guardring 51.

According to the present embodiment, since at least one of the firstshield wiring line S1, the second shield wiring line S2, and the thirdshield wiring line S3 is electrically connected to the guard ring 51,which is typically electrically connected to a stable potential, thewiring line 321, which electrically connects the passive filter 32 andthe amplification unit 33 to each other, can be shielded and kept at astable potential.

2. Electronic Apparatus

FIG. 6 is a functional block diagram of an electronic apparatus 1000according to the present embodiment. The same components as those in theembodiment described above have the same reference symbols and will notbe described in detail.

The electronic apparatus 1000 according to the present embodimentincludes the circuit 5 for a physical quantity detection device or thephysical quantity detection device 1. In the example shown in FIG. 6,the electronic apparatus 1000 includes the physical quantity detectiondevice 1, which includes the vibrator 10 and the circuit 5 for aphysical quantity detection device, a CPU (central processing unit)1010, an operation section 1020, a ROM (read only memory) 1030, a RAM(random access memory) 1040, a communication section 1050, a displaysection 1060, and a sound output section 1070. In the electronicapparatus 1000 according to the present embodiment, part of thecomponents (portions described above) shown in FIG. 6 may be omitted orchanged, or other components may be added.

The CPU 1010 carries out a variety of calculation processes and controlprocesses in accordance with a program stored, for example, in the ROM1030. Specifically, the CPU 1010 carries out a computation process basedon an output signal from the physical quantity detection device 1, avariety of processes according to operation signals from the operationsection 1020, a process of controlling the communication section 1050for data communication with an external apparatus, a process oftransmitting a display signal that causes the display section 1060 todisplay a variety of types of information, a process of causing thesound output section 1070 to output a variety of sounds, and otherprocesses.

The operation section 1020 is an input device formed, for example, ofoperation keys and button switches and outputs an operation signalaccording to user's operation to the CPU 1010.

The ROM 1030 stores programs, data, and other types of information inaccordance with which the CPU 1010 carries out the variety ofcalculation processes and control processes.

The RAM 1040 is used as a work area for the CPU 1010 and temporarilystores programs and data read from the ROM 1030, data inputted throughthe operation section 1020, results of computation executed by the CPU1010 in accordance with a variety of programs, and other data.

The communication section 1050 performs a variety of types of controlfor establishing data communication between the CPU 1010 and an externalapparatus.

The display section 1060 is a display device formed of an LCD (liquidcrystal display), an electrophoretic display, or any other type ofdisplay and displays a variety of types of information based on thedisplay signal inputted from the CPU 1010.

The sound output section 1070 is a loudspeaker or any other device thatoutputs sounds.

The electronic apparatus 1000 according to the present embodiment, whichincludes the circuit 5 for a physical quantity detection device capableof suppressing a detuning frequency component with noise resulting froma filter suppressed, can be highly reliable in operation.

The electronic apparatus 1000 may conceivably be any of a variety ofelectronic apparatus, for example, a personal computer (such as mobilepersonal computer, laptop personal computer, and tablet personalcomputer), a mobile phone or any other mobile terminal, a digital stillcamera, an inkjet-type liquid ejection apparatus (such as inkjetprinter), a router, a switch, or any other storage area network device,a local area network device, a device for a mobile terminal basestation, a television receiver, a video camcorder, a video recorder, acar navigation system, a pager, an electronic notebook (includingelectronic notebook having communication capability), an electronicdictionary, a desktop calculator, an electronic game console, a gamecontroller, a word processor, a workstation, a TV phone, a securitytelevision monitor, electronic binoculars, a POS (point of sale)terminal, medical apparatus (such as electronic thermometer, bloodpressure gauge, blood sugar meter, electrocardiograph, ultrasonicdiagnostic apparatus, and electronic endoscope), a fish finder, avariety of measuring apparatus, a variety of instruments (such asinstruments in vehicles, airplanes, and ships), a flight simulator, ahead-mounted display, a motion tracer, a motion tracker, a motioncontroller, and a PDR (pedestrian dead reckoning) device.

FIG. 7 shows an example of the exterior appearance of a smartphone as anexample of the electronic apparatus 1000. The smartphone as theelectronic apparatus 1000 includes buttons as the operation section 1020and an LCD as the display section 1060. The smartphone, which is theelectronic apparatus 1000 and includes the circuit 5 for a physicalquantity detection device capable suppressing a detuning frequencycomponent with noise resulting from a filter suppressed, can be highlyreliable.

3. Moving Object

FIG. 8 shows (is a top view showing) an example of a moving object 400according to the present embodiment. The same components as those in theembodiment described above have the same reference symbols and will notbe described in detail.

The moving object 400 according to the present embodiment includes thecircuit 5 for a physical quantity detection device or the physicalquantity detection device 1. FIG. 8 shows the moving object 400including the physical quantity detection device 1. In the example shownin FIG. 8, the moving object 400 includes a controller 420, a controller430, and a controller 440, which perform a variety of types of control,for example, on an engine system, a brake system, and a keyless entrysystem, a battery 450, and a backup battery 460. In the moving object400 according to the present embodiment, part of the components(portions described above) shown in FIG. 8 may be omitted or changed, orother components may be added.

The moving object 400 according to the present embodiment, whichincludes the circuit 5 for a physical quantity detection device capablesuppressing a detuning frequency component with noise resulting from afilter suppressed, can be highly reliable in operation.

The moving object 400 may conceivably be any of a variety of movingobjects, for example, an automobile (including electric automobile), ajet airplane, a helicopter, and other aircraft, a ship, a rocket, and anartificial satellite.

The present embodiment or the variations have been described above. Theinvention is not limited to the present embodiment or the variations andcan be implemented in a variety of aspects to the extent that they donot depart from the substance of the invention.

The scope of the invention encompasses substantially the sameconfigurations as the configuration described in the embodiment (forexample, a configuration having the same function, using the samemethod, and providing the same result or a configuration having the samepurpose and providing the same effect). Further, the scope of theinvention encompasses a configuration in which an inessential portion ofthe configuration described in the embodiment is replaced. Moreover, thescope of the invention encompasses a configuration that provides thesame advantageous effect as that provided by the configuration describedin the embodiment or a configuration that can achieve the same purposeas that achieved by the configuration described in the embodiment.Further, the scope of the invention encompasses a configuration in whicha known technology is added to the configuration described in theembodiment.

The entire disclosure of Japanese Patent Application No. 2013-226010,filed Oct. 30, 2013 is expressly incorporated by reference herein.

What is claimed is:
 1. A circuit for a physical quantity detectiondevice, the circuit comprising: a drive unit that generates a drivesignal, the drive signal causing a vibrator to vibrate; a detection unitthat detects a detection signal outputted from the vibrator based on thedrive signal; a passive filter which has a filter characteristic inwhich a cutoff frequency is lower than a detuning frequency and in whicha cutoff frequency band contains a frequency band higher than the cutofffrequency, a signal from the detection unit being inputted to thepassive filter; and an amplification unit that amplifies a signal fromthe passive filter.
 2. The circuit for a physical quantity detectiondevice according to claim 1, wherein the cutoff frequency is one-halfthe detuning frequency or lower.
 3. The circuit for a physical quantitydetection device according to claim 1, wherein the passive filter is afirst-order CR filter.
 4. The circuit for a physical quantity detectiondevice according to claim 1, wherein the passive filter is asecond-order or higher-order CR filter.
 5. The circuit for a physicalquantity detection device according to claim 1, further comprising afilter unit that filters a signal outputted from the amplification unit.6. The circuit for a physical quantity detection device according toclaim 1, further comprising: a semiconductor substrate; a wiring linethat is provided in the semiconductor substrate and electricallyconnects the passive filter and the amplification unit to each other;and a first shield wiring line that is provided in the semiconductorsubstrate so that the first shield wiring line is separated from thewiring line and juxtaposed to at least part of the wiring line in a planview.
 7. The circuit for a physical quantity detection device accordingto claim 6, further comprising a second shield wiring line that isprovided in the semiconductor substrate so that the second shield wiringline is separated from the wiring line and juxtaposed to at least partof the wiring line in the plan view, wherein the at least part of thewiring line is disposed between the first shield wiring line and thesecond shield wiring line in the plan view.
 8. The circuit for aphysical quantity detection device according to claim 6, furthercomprising a second shield wiring line that is provided in thesemiconductor substrate so that the second shield wiring line isseparated from the wiring line and overlaps with at least part of thewiring line in the plan view.
 9. The circuit for a physical quantitydetection device according to claim 7, further comprising a third shieldwiring line that is provided in the semiconductor substrate so that thethird shield wiring line is separated from the wiring line and overlapswith at least part of the wiring line in the plan view.
 10. The circuitfor a physical quantity detection device according to claim 9, furthercomprising a guard ring that is provided in the semiconductor substrateso that the guard ring surrounds an inner part of the circuit for aphysical quantity detection device in the plan view, wherein at leastone of the first shield wiring line, the second shield wiring line, andthe third shield wiring line is electrically connected to the guardring.
 11. A physical quantity detection device comprising: the circuitfor a physical quantity detection device according to claim 1; and thevibrator.
 12. An electronic apparatus comprising the circuit for aphysical quantity detection device according to claim
 1. 13. A movingobject comprising the circuit for a physical quantity detection deviceaccording to claim 1.